Amplifier

ABSTRACT

The present invention relates to an amplifier comprising a first amplification circuit (1) formed of a first transistor (10) and a second amplification circuit (2) formed of a second transistor (11), wherein a first filter (3) having a desired pass-band and a desired attenuation band is connected between the output section of the foregoing first amplification circuit (1) and the input section of the foregoing second amplification circuit (2), thereby reducing noises in the output.

TECHNICAL FIELD

The present invention relates to an amplifier for use in wirelesscommunication equipment such as a transmitter of portable telephone, forexample.

BACKGROUND ARTS

In general, an amplifier for communication equipment is required to havehigh efficiency and it is known that a matching circuit is used toachieve high efficiencies of an amplifier as disclosed in a JapanesePublished Unexamined Patent Application of No. 32335/95. When signalsare amplified by an amplifier, such undesired signal components as noiseand the like that exist outside the frequencies intended forAmplification are also amplified at the same time. Because of this, afilter is connected to the output side of an amplifier to attenuateundesired signal components such as noise and the like.

One of the problems involved with the foregoing system has been thatattenuation of the noise amplified by an amplifier and additional noiseshas to be achieved by a filter alone situated behind the amplifier inthe system, thereby requiring the filter to have large attenuation byusing many resonators resulting in a bulky filter. In addition, the lossin a pass-band of the filter connected behind the amplifier tends toincrease, thus requiring the amplifier to output more power withresultant hindrance to the efficiency improvement of the amplifier.

More specifically, the relations involved with band-pass filterattenuation vs. frequency characteristics, frequency spacings intransmitting signals and receiving signals, and the like will beexplained with reference to FIG. 14. FIG. 14 shows a case wherein areceiving signal band is located in a higher frequency band than atransmitting signal band. In general, with portable telephones, aplurality of both transmitting signal frequencies and receiving signalfrequencies are prepared within a given frequency band, therebycommunications being performed between transmitting signals andreceiving signals through a step of selecting a pair of frequencies, thefrequency spacing of which maintains a constant value. Also, signalsthat have passed a filter behind an amplifier are needed to suppressundesired signal components such as noise and the like existing in thereceiving signal frequencies in order to prevent a reduction inreceiving sensitivity caused by an infiltration of undesired signalsinto a receiving section. The general characteristics required of afilter that satisfies the foregoing requirement are to have a smallamount of attenuation in the transmitting frequency band and a largeamount of attenuation in the receiving frequency band, and to make theattenuation in the transmitting frequency band stay lower than thetolerated attenuation level of the transmitting signal at the highestfrequency and the attenuation in the receiving frequency band maintainthe needed attenuation of the receiving signal at the lowest frequency.As a result, the filter characteristics are required to have a largeamount of attenuation change for frequency changes, thereby causing, ingeneral, the filter characteristics to show large attenuation intransmitting signals and reduced amplification efficiencies.

DISCLOSURE OF THE INVENTION

The object of the present invention is to reduce noises outputted froman amplifier, thereby allowing a filter connected behind the amplifierto have less steep attenuation characteristics and at the same timeimproving efficiencies of the amplifier.

In order to achieve the foregoing object, an amplifier of the presentinvention comprises a first filter, which is connected between theoutput section of a first amplification circuit and the input section ofa second amplification circuit, has specified pass band and a specifiedattenuation band and show different values between input impedance andoutput impedance.

According to the structure as described in the above, the signalsintended for amplification and outputted from the first amplificationcircuit are inputted to the second amplification circuit almost withoutany attenuation while the noises outputted from the first amplificationcircuit being inputted to the second amplification circuit afterattenuation by the first filter. Thus, a very little amount of noises isoutputted from the second amplification circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit block diagram of an amplifier in an exemplaryembodiment of the present invention.

FIG. 2 shows characteristics of a filter of the foregoing amplifier.

FIG. 3 is a cross-sectional view of a specific structure of theforegoing amplifier.

FIG. 4 is a cross-sectional view of an amplifier in another exemplaryembodiment of the present invention.

FIG. 5 shows impedance characteristics of the foregoing amplifier.

FIG. 6 is a circuit block diagram of an amplifier in another exemplifiedembodiment of the present invention.

FIG. 7 is a pattern diagram of one of the filters for the foregoingamplifier.

FIG. 8 shows characteristics of another filter used in the foregoingamplifier.

FIG. 9 is a circuit block diagram of an amplifier in still anotherexemplary embodiment of the present invention.

FIG. 10 shows frequency characteristics of a frequency variable filterused in the foregoing amplifier.

FIG. 11 is a schematic circuit diagram of a filter used in the foregoingamplifier.

FIG. 12 shows how a band-pass amplifier with the foregoing filter builtwithin a substrate is structured.

FIG. 13 shows frequency characteristics of a band eliminating filterused in a band-pass amplifier of the present invention.

FIG. 14 shows frequency characteristics of a bandpass filter used in aprior art band-pass amplifier.

PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 is a circuit block diagram of an amplifier in an exemplaryembodiment of the present invention.

In FIG. 1, the reference numeral 1 shows a first amplification circuit,the output of which is connected to a first filter 3. Further, theoutput of the first filter 3 is connected to a second amplificationcircuit 2. A power supply terminal 6 is connected to the firstamplification circuit 1 and second amplification circuit 2, an inputterminal 4 is connected to the input of the first amplification circuit1 and an output terminal 5 is connected to the output of the secondamplification circuit 2.

According to the structure as described in the above, signals inputtedin the input terminal 4 are amplified at the first amplification circuit1 and then inputted to the first filter 3. At the same time, noisesinputted from the input terminal 4 are amplified at the firstamplification circuit 1 and inputted to the first filter 3. In addition,noises produced inside of the first amplification circuit 1 are alsoinputted to the first filter 3. In other words, noises having a highlevel are outputted from the first amplification circuit 1. However,when the first filter 3 is a band-pass filter as shown in FIG. 2, thesignals amplified at the first amplification circuit 1 (located in thetransmission band) are outputted with little attenuation while thenoises (located in the receiving band) are attenuated greatly. As aresult, signals of a high level and noises of only a minute level areoutputted from the second amplification circuit 2 to the output terminal5. Also, in the present exemplary embodiment, the loss in thetransmission band of the first filter 3 can be sufficiently compensatedby an improvement in amplification factor of the first amplificationcircuit 1. Efficiencies of the amplifier are rather enhanced since theoutput power of the second amplification circuit 2 can be reducedbecause of a reduction of the loss in the transmission band caused bymitigation of the amount of attenuation in noise required of the filterthat is connected behind the second amplification circuit 2. By the useof an amplifier of the present exemplary embodiment as the amplifier inthe transmission side of wireless communication equipment, powerconsumption can be reduced greatly.

FIG. 3 is a cross-sectional view of a specific structure of an amplifierof the present invention.

In FIG. 3, the reference numerals 10 and 11 are a first transistor andsecond transistor that form a first amplification circuit 1 and secondamplification circuit 2, respectively. Electrode patterns 14a to 14c aredisposed inside of a dielectric 13 and sandwiched between groundelectrodes 12a and 12b. A dielectric 15a is laid on top of the groundelectrode 12a, and further on top of the dielectric 15a electrodepatterns are formed and the first transistor 10 and second transistor 11are mounted, thus the first amplification circuit 1 and secondamplification circuit 2 are constructed. In addition, a dielectric 15bis laid on the bottom surface of the ground electrode 12b and further anelectrode pattern is formed on the surface of the dielectric 15b, thusproviding a terminal electrode 18. Electrode patterns 16a and 16b aresituated opposite to part of the electrode pattern 14a or the electrodepattern 14c with the dielectric 13 placed in between. Electrode patterns17a and 17b are situated opposite to the electrode pattern 16a and 16bwith the dielectric 15a placed in between, respectively. The electrodepattern 17a is connected with the output terminal of the firsttransistor 10 and the electrode pattern 17b is connected with the inputterminal of the second transistor 11. Through holes 19 are connectedwith the ground terminals of the first transistor 10 and secondtransistor 11 and also with the ground electrodes 12a and 12b.

According to the structure as described in the above, the first filter 3is formed of the electrode patterns 14a to 14c, the dielectric 13 aidthe ground electrodes 12a and 12b, as shown in FIG. 2. The outputterminal of the first transistor 10 is coupled with the first filter 3by the capacitance formed between the opposing electrode patterns 14a,16a and 17a. Also, the input terminal of the second transistor 11 iscoupled with the first filter 3 by the capacitance formed between theopposing electrode patterns 14c, 16b and 17b in the same manner asabove. Thus, a circuit block as shown in FIG. 1 can be constructed and afilter can be miniaturized by employing a multi-layer structure as inthe present exemplary embodiment. Also, heat dissipation can be improvedby having the ground terminals of the first transistor 10 and secondtransistor 11 connected with the ground electrodes 12a and 12b by meansof the through holes 19. In addition, it is preferred that thedielectric constant of the dielectric 13 is not less than 10 forminiaturization of the filter and the dielectric constant of thedielectrics 15a and 16b does not exceed 10 for easier construction ofcircuits. In case where the structure in the present exemplaryembodiment is formed by use of multi-layered green sheets and a batchsintering process, the dielectrics 15a and 15b are to be formed of thesame material and to the same thickness so that the sintering may beperformed without causing any danger of warping.

FIG. 4 is a cross-sectional view of an amplifier in another exemplaryembodiment of the present invention.

In FIG. 4, the reference symbols 20a and 20b are recesses formed byrunning through part of the dielectric 15a. The first and secondtransistors 10 and 11 are mounted inside of the recesses 20a and 20b,respectively, and the ground terminals thereof are directly connected tothe ground electrode 12a, thereby contributing further to an increase inheat dissipation.

Furthermore, in FIG. 3 and FIG. 4, the same effect as above can begained by connecting one of the spacings selected from the ones betweenthe electrode patterns 14a and 16a and between the electrode patterns16a and 17a by a via hole and leaving the remaining spacing to formcapacitance. Similarly, the same can be achieved by connecting one ofthe spacings selected from the ones between the electrode patterns 14cand 16b and between the electrode patterns 16b and 17b by a via hole andleaving the remaining spacing to form capacitance in FIG. 3 and FIG. 4.

FIG. 5 is a diagram to show input and output impedance of the firstfilter 3 in FIG. 1.

In FIG. 5, the reference numeral 21 shows a domain of input and outputimpedance for the first transistor 10 or the second transistor 11, andthe reference numeral 22 is a domain of input and output impedance forthe first filter 3. Since a transistor used in an amplifier at thetransmission side of communication equipment outputs a large power, theinput and output impedance thereof is low as indicated in FIG. 5.Therefore, the loss incurred by coils and capacitors that are usuallyused in a matching circuit can be eliminated, thereby improvingefficiencies by making the input and output impedance of the firstfilter 3 employed in the present invention not 50 ohms but a valuebetween 1/2 and 2 times the real part of the output impedance of thefirst transistor 10 or the input impedance of the second transistor 11and also by connecting the first transistor 10 and second transistor 11directly with the first filter 3. In other words, when the input andoutput impedance of the first transistor 10 and second transistor 11falls in the domain 21 of FIG. 5, it is preferred that the input andoutput impedance of the first filter 3 is made to fall in the domain 22of FIG. 5. Also, when the first filter 3 is structured according to FIG.3 and FIG. 4 and connected with the first transistor 10 and secondtransistor 11, the input and output impedance of the first filter 3 canbe made a complex conjugate of the first transistor 10 and secondtransistor 11 depending on the opposing areas between the electrodepatterns 14 and 16 and between the electrode patterns 16 and 17.Further, the input and output impedance of the first filter 3 can be setup independently according to the impedance of each respectiveamplification circuit connected thereto.

FIG. 6 is a circuit block diagram of an amplifier in another exemplifiedembodiment of the present invention and FIG. 7 shows how the foregoingcircuit block is structured.

In FIG. 6, the reference numeral 23 is a second filter connected betweenthe output of the second amplification circuit 2 and the output terminal5. In FIG. 7, the reference numerals 24 and 25 are electrode patternsformed inside of the dielectric 13 as shown in FIG. 3 and FIG. 4. Thereference numeral 26 shows through holes connected between the groundelectrodes 12a and 12b.

In the structure as described in the above, the second filter 23 hardlyattenuates the desired signals outputted from the second amplificationcircuit 2 and attenuates noises, instead. Since the input impedance ofthe second filter 23 is set to 1/2 to 2 times the real part of theoutput impedance of the second transistor 11, the second filter 23 canbe connected directly with the second transistor 11. As a result,efficiencies of the second amplification circuit 2 can be enhanced. Inaddition, when the first filter 3 and second filter 23 are formed ofstrip lines that compose the electrode patterns 24 and 25 in one planeof a laminated structure as shown in FIG. 7, coupling betweenthe-electrode patterns 24 and 25 can be prevented from taking place byproviding the through holes 26, which are connected with the groundelectrodes 12a and 12b, between the electrode patterns 24 and 25. Inthat case, the aforementioned coupling can be extremely reduced bymaking the spacing between the through holes 26 shorter than the lengthof the shortest line in the electrode patterns 24 and 25. Furthermore,the coupling between the electrode patterns 24 and 25 can be furtherreduced by arranging the electrode patterns 24 and 25 in a positionperpendicular to each other.

Further, the characteristics of the first filter 3 and second filter 23can incorporate the characteristics of a bandpass filter whereby signalsof communication equipment in a transmission band are passed and signalsin a receiving band are attenuated as shown in FIG. 2, and also canincorporate the characteristics of a band rejection filter and the likewhereby signals in a receiving band are attenuated as shown in FIG. 8.

It is also possible to attach to the amplifier a function that allowsthe amplifier to be used as a monitor for power controlling byintegrating in one piece with the amplifier a directional coupler thatutilizes a two parallel wire transmission line of a laminated structure,thereby allowing power to be taken out of a desired position of theamplifier.

FIG. 9 is a circuit block diagram of an amplifier in still anotherexemplary embodiment of the present invention, wherein the referencenumeral 31 is a first amplification circuit, the reference numeral 32 isa second amplification circuit, the reference numeral 33 is a frequencyvariable filter, the reference numeral 34 is a computing circuit, thereference numeral 35 is a voltage controlled oscillator, the referencenumeral 36 is an input terminal and the reference numeral 37 is anoutput terminal.

Transmission signals are inputted into the input terminal 36, amplifiedin the first amplification circuit 31 and second amplification circuit32 and pass through the frequency variable filter 33, thereby suchundesired signals as noises and the like that exist in the receivingsignal frequencies being suppressed, and are outputted through theoutput terminal 37. Frequency characteristics of the frequency variablefilter 33 are controlled by a control voltage produced by processing inthe computing circuit 34 an input frequency control voltage of thevoltage controlled oscillator 35 which is inputted into the computingcircuit 34. The frequency variable filter 33 is directly connected tothe output section of the second amplification circuit 32, and in thesame way as described in FIG. 1 the input impedance of the frequencyvariable filter 33 is adjusted to match with the output impedance of thesecond amplification circuit 32 and differs from the output impedance ofthe frequency variable filter 33.

FIG. 10 shows frequency characteristics of the frequency variable filter33 In terms of attenuation vs. frequency. A solid line shows a casewherein transmission signals have the lowest frequency in the frequencyband, and a dash and dotted line shows a case wherein transmissionsignals have the highest frequency in the frequency band. A dotted lineshows attenuation vs. frequency characteristics of a prior art filterwherein frequency characteristics are not variable. In all the cases asdescribed in FIG. 10, the receiving signals have a higher frequency thanthe transmission signals and the transmission frequency signals have thelowest frequency in the transmission frequency band.

When the frequency variable filter 33 is connected to the output side ofthe second amplification circuit 32 as in the present exemplaryembodiment, it suffices that only the signals with frequencies used intransmission are suppressed below the tolerated attenuation level and,according to the changes in transmission frequency, filter's frequencycharacteristics are changed to match with transmission signals.Therefore, the frequency characteristics of filter's attenuation areallowed to have a smaller degree of changes in attenuation againstfrequency changes, resulting in a reduction of attenuation at thetransmission section and an increase in amplification efficiencies.Accordingly, a high efficiency band-pass amplifier can be realized.

Although the present exemplary embodiment deals with a case wherein theamplification circuit 32 is connected to the input side of the frequencyvariable filter 33, the same effect can be obtained by connecting theamplification circuit 32 to the output side of the frequency variablefilter 33 as shown in FIG. 9A. The frequency variable filter 33 isdirectly connected to the input section of the first amplificationcircuit 31 and also the output section of the second amplificationcircuit 32, and in the same way as described in FIG. 1 the inputimpedance of the frequency variable filter 33 is adjusted to match withthe output impedance of the first amplification circuit 31 and theoutput impedance of the frequency variable filter 33 is made to matchwith the input impedance of the second amplification circuit 32, therebymaking the input impedance and output impedance of the frequencyvariable filter 33 different from each other. In this case, it isneedless to say that by connecting a second frequency variable filterdirectly to the output of the second amplification circuit 32 in thesame way as in FIG. 6, efficiencies of the second amplification circuit32 can be improved. At this time, in the same way as described in FIG. 6the input impedance of the second frequency variable filter is adjustedto match with the output impedance of the second amplification circuit32.

FIG. 11 is a typical schematic circuit diagram of a frequency variablefilter, wherein the reference numerals 41 to 44 are interstage couplingcapacitors, the reference numerals 45 to 47 are varactor diodes, thereference numerals 48 to 50 are resonance capacitors, the referencenumerals 51 to 53 are resonance coils, the reference numeral 54 is aninput terminal and the reference numeral 55 is an output terminal.

Transmission signals are inputted into the input terminal 54 andoutputted from the output terminal 55 after being attenuated accordingto frequency characteristics like the ones as described in FIG. 10, forexample. In this case, the filter's frequency characteristics aredetermined according to a resonant frequency fixed by the resonancecapacitor 48 and resonance coil 51, a resonant frequency fixed by theresonance capacitor 49 and resonant coil 52, a resonant frequency fixedby the resonance capacitor 50 and resonance coil 53 and the interstagecoupling capacitors. When capacitance of the varactor diode 45 ischanged, the total capacitance value of the foregoing capacitance andthe capacitance of the resonance capacitor 48 is changed, resulting in achange of the resonant frequency that is determined by the foregoingtotal capacitance and the resonance coil 51. The varactor diodes 46 and47 play the roles similar to the one played by the varactor diode 45.Accordingly, by changing the capacitance of the varactor diodes 45 to47, the characteristics of the frequency variable filter can be changedas described in FIG. 10.

Although the present exemplary embodiment has dealt with a case whereina resonator section was formed of resonance capacitors and resonancecoils, the same effects can be achieved by the use of planar typeresonators.

FIG. 12 shows a specific structure in another exemplary embodiment ofthe present invention, wherein the reference numerals 61 to 63 arevaractor diodes, the reference numerals 64 to 66 are resonators, thereference numeral 67 is a control signal input terminal, the referencenumeral 68 is an input terminal, the reference numerals 69 and 70 areamplification circuits, the reference numeral 71 is an output terminaland the reference numerals 72 and 73 are shields.

Transmission signals are inputted through the input terminal 68 andamplified by the amplification circuits 69 and 70. Then, the amplifiedtransmission signals are attenuated at a frequency variable filtersection formed of the varactor diodes 61 to 63, resonators 64 to 66 andthe control signal input terminal 67 in accordance with frequencycharacteristics as described in FIG. 10, for example, and outputted fromthe output terminal 71. The varactor diode 61 has a role to change theresonant frequency of the resonator 64, the varactor diode 62 has a roleto change the resonant frequency of the resonator 65 and the varactordiode 63 has a role to change the resonant frequency of the resonator66. Input control signals inputted through the control signal inputterminal 67 change the capacitance of the varactors 61 to 63 and causethe resonant frequencies of the resonators 64 to 66 to change, therebyhaving the frequency characteristics of the frequency variable filterchanged.

Although the present exemplary embodiment has dealt with a case whereina band-pass filter was used, the same effects can be obtained by the useof a band rejection filter as shown in FIG. 13.

In addition, although the present exemplary embodiment has dealt with acase wherein a transmission amplifier for portable telephones was used,the same effects can be obtained by the use of the technologies of thepresent invention in transmission amplifiers in the equipment forcommunications and broadcasting used in the base stations of portabletelephones, satellite communications and the like.

INDUSTRIAL APPLICATIONS

As described in the above, the present invention is characterized byconnecting a first filter between the output section of a firstamplification circuit of an amplifier and the input section of a secondamplification circuit of the amplifier. Accordingly, the desired signalsoutputted from the first amplification circuit are hardly attenuated inthe first filter and inputted into the second amplification circuit, butnoises outputted from the first amplification circuit are attenuated inthe first filter and inputted into the second amplification circuit.Therefore, only a very small amount of noises is outputted from thesecond amplification circuit.

According to the present invention as described in the foregoing, sincea frequency variable filter wherein frequency characteristics arechanged in accordance with passing signals is connected to the outputside of an amplifier, the attenuation characteristics can be made lesssteep and the attenuation magnitude can be made small, thereby enablingto increase the overall efficiencies of the amplifier including thefilter. In addition, since the control of the frequency characteristicsof the frequency variable filter is performed by utilizing frequencycontrol voltages of a voltage controlled oscillator, a downsizing of theamplifier is made possible. Moreover, by having the frequency variablefilter built inside of the substrate of the amplifier, a furtherdownsizing of the amplifier is made possible when compared with a casewherein the amplifier and filter are produced separately. Also, by theuse of a different type of substrate, the dielectric constant of thefrequency variable filter section can be increased, thereby enabling todownsize the amplifier further.

What is claimed is:
 1. An amplifier having a first filter, which has adesired pass-band and a desired attenuation band and also has adifference between input impedance and output impedance by adjusting theinput impedance to a value between 1/2 to 2 times the real part ofoutput impedance of a first transistor and the output impedance to avalue between 1/2 to 2 times the real part of input impedance of asecond transistor, directly connected between the output terminal of thefirst transistor and the input terminal of the second transistor,whereinthe first filter is formed so as to have electrode patterns built in adielectric of a relative dielectric constant exceeding 10 inclusive thatis sandwiched between ground electrodes on the upper and bottom surfacesthereof, electrode patterns are formed over said ground electrode on theupper surface of said dielectric with a dielectric material of arelative dielectric constant not exceeding 10 placed in between and afirst amplification circuit and a second amplification circuit aremounted on said electrode patterns.
 2. An amplifier having a firstfilter, which has a desired pass-band and a desired attenuation band andalso has a difference between input impedance and output impedance byadjusting the input impedance to a value between 1/2 to 2 times the realpart of output impedance of a first transistor and the output impedanceto a value between 1/2 to 2 times the real part of input impedance of asecond transistor, directly connected between the output terminal of thefirst transistor and the input terminal of the second transistor,whereinthe first filter is formed so as to have electrode patterns built in adielectric of a relative dielectric constant exceeding 10 inclusive thatis sandwiched between ground electrodes on the upper and bottom surfacesthereof, electrode patterns are formed over said ground electrode on theupper surface of the dielectric with a dielectric material of a relativedielectric constant not exceeding 10 placed in between, a firstamplification circuit and a second amplification circuit are mounted onsaid electrode patterns and also a part of terminal electrodes is formedover said ground electrode on the bottom surface of said dielectric witha dielectric material of a relative dielectric constant not exceeding 10placed in between.
 3. An amplifier having a first filter, which has adesired pass-band and a desired attenuation band and also has adifference between input impedance and output impedance by adjusting theinput impedance to a value between 1/2 to 2 times the real part ofoutput impedance of a first transistor and the output impedance to avalue between 1/2 to 2 times the real part of input impedance of asecond transistor, directly connected between the output terminal of thefirst transistor and the input terminal of the second transistor;whereinthe first filter is formed so as to have electrode patterns built in adielectric sandwiched between ground electrodes on the upper and bottomsurfaces thereof, wherein the first filter and amplification circuitsare coupled by capacitance formed between opposing electrodes that havea dielectric material placed in between.
 4. The amplifier according toclaim 3, wherein the respective first and second transistors are mountedin recesses formed on the surface of the dielectric material.
 5. Theamplifier according to claim 3, wherein an electrode pattern connectedwith the ground terminals of the respective first and second transistorsis connected to the upper and bottom ground electrodes by means ofthrough holes.
 6. The amplifier according to claim 3, wherein adirectional coupler formed of electrode patterns is provided inside of adielectric of a relative dielectric constant exceeding 10 inclusive oron the surface of a dielectric of a relative dielectric constant notexceeding
 10. 7. The amplifier according to claim 4, wherein thedielectric materials of a relative dielectric constant not exceeding 10that are used on the upper surface of the upper side ground electrodeand on the bottom surface of the bottom side ground electrode are madeof the same material and also made the same in thickness.
 8. Anamplifier having a first filter, which has a desired pass-band and adesired attenuation band and also has a difference between inputimpedance and output impedance by adjusting the input impedance to avalue between 1/2 to 2 times the real part of the output impedance of afirst transistor and the output impedance to a value between 1/2 to 2times the real part of the input impedance of a second transistor,directly connected between the output terminal of the first transistorand the input terminal of the second transistor, and further having asecond filter, which has the same desired pass-band and desiredattenuation band as said first filter has and also has a differencebetween input impedance and output impedance by adjusting the inputimpedance to a value between 1/2 to 2 times the real part of the outputimpedance of the second transistor, directly connected to the outputterminal of said second transistor,wherein the respective first andsecond filters are formed so as to have electrode patterns built in adielectric of a relative dielectric constant exceeding 10 inclusive thatis sandwiched between ground electrodes on the upper and bottom surfacesthereof, electrode patterns are formed over said ground electrode on theupper surface of said dielectric with a dielectric material of arelative dielectric constant not exceeding 10 placed in between and thefirst amplification circuit and second amplification circuit are mountedon the electrode patterns.
 9. An amplifier having a first filter, whichhas a desired pass-band and a desired attenuation band and also has adifference between input impedance and output impedance by adjusting theinput impedance to a value between 1/2 to 2 times the real part ofoutput impedance of a first transistor and the output impedance to avalue between 1/2 to 2 times the real part of input impedance of asecond transistor, directly connected between the output terminal of thefirst transistor and the input terminal of the second transistor,whereinthe respective first and second filters are formed so as to haveelectrode patterns built in a dielectric of a relative dielectricconstant exceeding 10 inclusive that is sandwiched between groundelectrodes on the upper and bottom surfaces thereof, electrode patternsare formed over said ground electrode on the upper surface of saiddielectric with a dielectric material of a relative dielectric constantnot exceeding 10 placed in between, the first amplification circuit andsecond amplification circuit are mounted on said electrode patterns andalso a part of terminal electrodes is formed over said ground electrodeon the bottom surface of said dielectric with a dielectric material of arelative dielectric constant not exceeding 10 placed in between.
 10. Anamplifier having a first filter, which has a desired pass-band and adesired attenuation band and also has a difference between inputimpedance and output impedance by adjusting the input impedance to avalue between 1/2 to 2 times the real part of output impedance of afirst transistor and the output impedance to a value between 1/2 to 2times the real part of input impedance of a second transistor, directlyconnected between the output terminal of the first transistor and theinput terminal of the second transistor,wherein the respective firstfilter and second filter are formed so as to have electrode patternsbuilt in a dielectric sandwiched between ground electrodes on the upperand bottom surfaces thereof, wherein the respective first and secondfilters and amplification circuits are coupled by capacitance formedbetween opposing electrodes with a dielectric material placed inbetween.
 11. The amplifier according to claim 8, wherein the respectivefirst and second transistors are mounted in recesses formed on thesurface of the dielectric material.
 12. The amplifier according to claim8, wherein an electrode pattern connected with the ground terminals ofthe respective first and second transistors is connected to the upperand bottom ground electrodes by means of through holes.
 13. Theamplifier according to claim 8, wherein a directional coupler formed ofelectrode patterns is provided inside of a dielectric of a relativedielectric constant exceeding 10 inclusive or on the surface of adielectric of a relative dielectric constant not exceeding
 10. 14. Anamplifier having a first filter, which has a desired pass-band and adesired attenuation band and also has a difference between inputimpedance and output impedance by adjusting the input impedance to avalue between 1/2 to 2 times the real part of output impedance of afirst transistor and the output impedance to a value between 1/2 to 2times the real part of input impedance of a second transistor, directlyconnected between the output terminal of the first transistor and theinput terminal of the second transistor,wherein the respective firstfilter and second filter are formed so as to have electrode patternsbuilt in a dielectric sandwiched between ground electrodes on the upperand bottom surfaces thereof, wherein a plurality of through holes or viaholes connected to the upper side ground electrode and bottom sideground electrode are provided between the first filter and the secondfilter.
 15. An amplifier having a first filter, which has a desiredpass-band and a desired attenuation band and also has a differencebetween input impedance and output impedance by adjusting the inputimpedance to a value between 1/2 to 2 times the real part of outputimpedance of a first transistor and the output impedance to a valuebetween 1/2 to 2 times the real part of input impedance of a secondtransistor, directly connected between the output terminal of the firsttransistor and the input terminal of the second transistor,wherein therespective first filter and second filter are formed so as to haveelectrode patterns built in a dielectric sandwiched between groundelectrodes on the upper and bottom surfaces thereof, wherein the firstfilter and second filter are formed of strip lines and the strip linesof the first filter are arranged to be perpendicular to the strip linesof the second filter in direction.
 16. The amplifier according to claim8, wherein the respective first and second filters are used as aband-pass filter, a transmission band of communication equipment is thepassing band of said band-pass filter and a receiving band ofcommunication equipment is the attenuation band of said band-passfilter.
 17. The amplifier according to claim 13, wherein the spacingbetween the through holes or via holes connected to the upper side andbottom side ground electrodes is made smaller than the length of striplines of the first and second filters.
 18. An amplifier having a firstfrequency variable filter, which has a desired pass-band and a desiredattenuation band and has a difference between input impedance and outputimpedance by adjusting the input impedance to a value between 1/2 to 2times the real part of the output impedance of a first transistor andalso by adjusting the output impedance of a first filter to a valuebetween 1/2 to 2 times the real part of the input impedance of a secondtransistor directly connected between the output terminal of the firsttransistor and the input terminal of the second transistor and having afrequency control voltage of a voltage controlled oscillator used as thecontrol voltage of said frequency variable filter;wherein a computingcircuit to compute a control voltage for the first frequency variablefilter in accordance with a frequency control voltage of the voltagecontrolled oscillator is connected between the voltage controlledoscillator and the control voltage application terminal of the firstfrequency variable filter.
 19. The amplifier according to claim 18,wherein the first frequency variable filter is used as a band-passfilter, a transmission band of communication equipment is the passingband of said band-pass filter and a receiving band of communicationequipment is the attenuation band of said band-pass filter.
 20. Theamplifier according to claim 18, wherein the first frequency variablefilter is used as a band rejection filter and a receiving band ofcommunication equipment is the rejection band of said band rejectionfilter.
 21. The amplifier according to claim 18, wherein varactor diodesare used as the impedance variable elements of the first frequencyvariable filter.
 22. An amplifier having a first frequency variablefilter, which has a desired pass-band and a desired attenuation band andhas a difference between input impedance and output impedance byadjusting the input impedance to a value between 1/2 to 2 times the realpart of the output impedance of a first transistor and also by adjustingthe output impedance of a first filler to a value between 1/2 to 2 timesthe real part of the input impedance of a second transistor, directlyconnected between the output terminal of the first transistor and theinput terminal of the second transistor and having a frequency controlvoltage of a voltage controlled oscillator used as the control voltageof said frequency variable filter,wherein resonators of the firstfrequency variable filter are formed inside of a multilayered substrateand a circuit section of the frequency variable filter and anamplification circuit are formed on the surface of the substrate,thereby integrating the whole assembly in one-piece.
 23. The amplifieraccording to claim 1, wherein the multilayered substrate is formed of aplurality of layers, each having properties different from one another.24. An amplifier having a first frequency variable filter, which has adesired pass-band and a desired attenuation band and has a differencebetween input impedance and output impedance by adjusting the inputimpedance to a value between 1/2 to 2 times the real part of the outputimpedance of a first transistor and also by adjusting the outputimpedance of a first filter to a value between 1/2 to 2 times the realpart of the input impedance of a second transistor, directly connectedbetween the output terminal of the first transistor and the inputterminal of the second transistor and further having a second frequencyvariable filter, which has the same desired pass-band and desiredattenuation band as said first frequency variable filter has and has adifference between input impedance and output impedance by adjusting theinput impedance to a value between 1/2 to 2 times the real part of theoutput impedance of a second transistor, directly connected to theoutput terminal of the second transistor and having a frequency controlvoltage of a voltage controlled oscillator used as the control voltageof said first and second frequency variable filters;wherein a computingcircuit to compute a control voltage for the first and second-frequencyvariable filters in accordance with a frequency control voltage of thevoltage controlled oscillator is connected between the voltagecontrolled oscillator and the control voltage application terminal ofthe respective first and second frequency variable filters.
 25. Theamplifier according to claim 24, wherein the respective first and secondfrequency variable filters are used as a band-pass filter, atransmission band of communication equipment is the passing band of saidband-pass filters and a receiving band of communication equipment is theattenuation band of said band-pass filters.
 26. The amplifier accordingto claim 24, wherein the second frequency variable filter is used as aband rejection filter and a receiving band of communication equipment isthe rejection band of said band rejection filter.
 27. The amplifieraccording to claim 24, wherein varactor diodes are used as the impedancevariable elements of the first and second frequency variable filters.28. An amplifier having a first frequency variable filter, which has adesired pass-band and a desired attenuation band and has a differencebetween input impedance and output impedance by adjusting the inputimpedance to a value between 1/2 to 2 times the real part of the outputimpedance of a first transistor and also by adjusting the outputimpedance of a first filter to a value between 1/2 to 2 times the realpart of the input impedance of a second transistor, directly connectedbetween the output terminal of the first transistor and the inputterminal of the second transistor and further having a second frequencyvariable filter, which has the same desired pass-band and desiredattenuation band as said first frequency variable filter has and has adifference between input impedance and output impedance by adjusting theinput impedance to a value between 1/2 to 2 times the real part of theoutput impedance of a second transistor, directly connected to theoutput terminal of the second transistor and having a frequency controlvoltage of a voltage controlled oscillator used as the control voltageof said first and second frequency variable filters,wherein resonatorsof the first and second frequency variable filters are formed inside ofa multilayered substrate and a circuit section of the respective firstand second frequency variable filters and an amplification circuit areformed on the surface of the substrate, thereby integrating the wholeassembly in one-piece.
 29. The amplifier according to claim 21, whereinthe multilayered substrate is formed of a plurality of layers, eachhaving properties different from one another.